This invention relates generally to apparatus for trimming the uneven edges from drawn and ironed tubular metal bodies, such as aluminum or steel cans, and disposing of the scrap.
Specifically, it relates to trimmers of the type generally described in U.S. Pat. No. 3,425,251 to J. H. Maytag, entitled Can Trimmer and Scrap Disposing Mechanism. Trimmers of this type, which are used primarily for trimming of cans, have evidenced many problems which have made their operation unsatisfactorily inefficient and which have led to defects in cans.
Trimmers of this type have two main parallel shafts. A spindle is formed at a free end of one of these shafts. Can bodies are mounted over the spindle, which has a cutter and a knurling roller associated therewith. A tool wheel, carrying a cutter sector and a spaced knurling sector, is mounted on the second of the main shafts. The cutter sector and the knurling sector cooperate with the cutter and knurling roller, respectively, to sever an endless ring (which includes the uneven edge) of scrap from a can and cut, corrugate and discard the scrap ring from the area of operation.
As previously indicated, there are many problems with such apparatus. In particular, previously known devices of this type have caused many defects in trimmed container bodies. Most of these defects are imperfections in the trimmed edge, many of which can lead to more obviously critical defects at the time of seaming a container end to the container body. Such seaming puts much stress on the container edge and tiny defects can result in an unusable container.
A greater number of these defects result from the type of mandrel used to support a can body during trimming and knurling, and the configuration and orientation of the cutter and knurling roller used. The prior known devices exhibited a great deal of axial instability which often led to somewhat random dimensions and accompanying defects. A related problem was the lack of positive drive rotation of the container bodies on the spindle because of an inconsistent material pinch between the mandrel and the loading cylinder used for holding the container body on the mandrel during trimming.
A further related problem was the difficulty of spindle adjustment to accomodate tubular bodies of varying sizes. Another problem related to the existence of "stumbling points" on the spindle which had a tendency to introduce serious container defects.
Still another problem in prior known trimmers of this general type is caused by the knurling apparatus used to sever the trimmed endless ring of scrap. Such knurled scrap had a tendency to be uncontrolled in the direction in which it was discarded. In a high speed operation, this condition could sometimes result in scrap contacting the edge of a trimmed can which would cause an imperfection which later could result in a defect during seaming. It could also interfere with the operation in other apparent ways.